Refrigeration process



Patented Feb. 19, 1935 The present invention which REFRIGERATION raocass Ernest B. Miller and Gerald G.

Connolly, Baltimore, Md, assignors, by mesne assignments, to

Chester F. Hockley, receiver Corporation, Baltimore, Md

- Maryland No Drawing.

10 Claims.

is a continuation in part of our applications, Serial No. 427,649,

filed February '11,v 1930; Serial and Serial No.

July 23, 1930; ceinber 6, 1930; relat 500,666, filed Dees to refrigeration and more particularly to the type wherein the cooling ef fect is obtained by the evaporation of a liquid,

and the vapor is taken up in a solid sorbent. Y

porous ad- Befrigeration systems of this type may comprise an evaporator or cooling chamber,-containing the liquid to be evaporated or. fluid evaporated by expansion through an orifice, an adsorber containing the adsorbing material, and a condenser for condensing the vapor driven off from the adsorbing to said evaporator or material and returning it cooling chamber. -Where solid adsorbent material is employed for taking up the vapor from the cooling sorption must be effected in the substantially total absence. of permanent gases,

or the rate of adsorption will be so reduced that an efiective cooling will not be paratus suitable shown -in Figure 2 1,729,081, granted Various liquids secured. One form of apfor the present invention is of United States Patent September 24, 1929. may be employed in systems of this type, for instance, sulphur dioxid water,

ammonia, butane,

such as methylamine, et'hylamine, etc. Likewise,

tri-methvlamine, bents may be used,

gels such as the gels methyl chloride, and amines dimethylamine, various adsorfor example, hard, porous of silica, tungsten oxide,

aluminum oxide, etc., and gels consisting of two or more of these oxides, activated charcoal, etc.

However, not all of ployed with any one the adsorbents can be emliquid, and, vice versa, not

all of the liquids can be employed with any one adsorbent.

Many of. the combinations of adsorbent and liquid will operate at first, but after repeated cycles either there is a breaking down of the vapor, gradually forming permanent gases, or else there is a reaction between the vapor and ,adsorbefit that reduces 45 the adsorbing materi Tests have shown that gel as the adsorbent as the liquid, after so satisfactory and sulphur dioxide,

the adsorptive power of al'.

the combination of silica and ammonia or an amine repeated activations, is not as the combination of silica gel or silica gel and water. It

is thought that wth the ammonia or aminesilica gel syste and perhaps perman action on the gel'injures it,

ent gases are formed.

The principal feature of the present invention is the provision of an adsorption refrigerachamber, the adfor The Silica Gel a corporation of Application June 9, 1931, Serial No. 543,240

tion system that operates successfully with a solid, porous adsorbent and ammonia or an No. 470,227, filed amine According to the present invention it has been found that no'harmful efiects occur if the adsorbent has its moisture content reduced to such point that no reaction injurious to the adsorbent occurs when in use in the system.

The solid, porous adsorbent may be a plain dried'gel containing only one hydrous oxide such as the oxide of iron, chromium, bismuth, aluminum, gallium, copper, nickel, beryllium, um, indium, zirconium,

thorium, cerium, scandium, vanadium, manganese, silicon, germani tin, tantalum,

molybdenum, tungsten,

or the like,

or mixtures of any of said oxides, treated as by activation to reduce the water content to such point that no reaction injurious thereto occurs when used to adsorb dry the refrigerating cycle previously The hydrous oxides of silicon, titanium, talum, molybdenum,

are best prepared by reacting the informing the desired hydrous vanadium,

'gredients capable of ammonia or amine in described.

oxide gels, such as those of the germanium, tin, tantungsten, and pentavalent gel under such conditions as to form an intermediate reaction product which is acid and treating such reaction product so as to convert it into the dried gel.

The hydrous oxide gels, such as those of the oxides gallium, indium, 'tanium, zirconium, thorium,

and tetravalent vanadium,

manganese,

made by reacting forming the desired ditions such as to product which is action product so as to convert it into the dried gel.

from

of iron, chromium. aluminum, copper, nickel, beryllium, ti-

cerium, scandium, are best the ingredients .capable of hydrous oxide gel under conform an intermediate reaction alkaline, and treating such 're- Where it is desired to use a plain gel obtained an intermediate reaction product which is acid, like silica, tungstia, stannia, titaniagels,

etc., or mixed gels of said content should 3% .to 4% Of its dry oxides, the moisture be below 5%, preferably about weight. If the plain gel to be employed is one obtained from an intermediate reaction product which is alkaline, as

for instance, aluminum, chromium, iron oxide gels,

vanadium, etc., or mixtures of said oxides,

the moisture content may be as high as 10% of its dry weight. In place of a hydrous oxides,

dried gel containing one or more a material having a pore structitani-' I ture similar to a dried gel such as base exchange compounds, activated carbon, treated as by activation to reduce the moisture content to such point that no reaction injurious thereto occurs when used to adsorb dry ammonia or amine in the refrigerating cycle, may be employed. If desired, a dried gel containing one or more hydrous oxides admixed with activated carbon, a gel having a filler of the adsorbent type such as Bentonite associated therewith, or non-homogeneous gels containing one or more hydrous oxides, may also be used. The base exchange compounds may be the natural occurring compounds such as glauconite, suitable natural zeolites and the like, or the artificially prepared compounds, for instance, sodium chromium silicate, potassium boron silicate, sodium vanadium silicate, and the like, or the porous structure remaining after leaching the base exchange compound with either acid or water. Of the base exchange compounds, the artificially prepared compounds derived via a hydrogel or gelatinous precipitate are preferably used. The moisture content of the base exchange compounds, activated carbon, and the other aforementioned materials should be reduced to a point below 10% of their dry weight.

In order to reduce the water content of the gel,,base exchange compound, or like material, to this low amount, it is heated to temperatures between 375 and 450 C. for 2 or 3 hours, although in the refrigerating cycle the activating temperature of the adsorbent rarely exceeds 233 C.

Where it is desired to use an amine as the refrigerant, methylamine is preferably employed.

As a specific example of the adsorbent material which may be used in the process of the present invention, reference may be had to silica gel. This may be prepared in any suitable manner, for instance, in accordance with the instructions given in the Patrick Patent 1,297,724, as by adding, with agitation, a solution of sodium silicate to an equal volume of an acid solution, such as a 10% solution by weight of hydrochloric acid, the specific gravity of the silicate solution being about 1.185. The ratio of SiO: to NazO, in the silicate solution may be as in any commercial solution, about 3.25 to 1. After a time the reaction mixture or sol, as it is called, sets to a homogeneous jelly-like mass termed a hydrogel. This is broken into pieces and washed with water, preferably at to 175 F., to remove salt and acid. The hydrogel is then dried in a current of air at 200 C. Before charging the refrigerating apparatus with the silica gel it is activated at 375 to 450 C. to reduce the moisture to a low point, say not more than 5%, preferably 3 to 4% of the dry product by weight.

with the low moisture content, there is no, or insufllcient, reaction to injure the gel.

Another specific adsorbent material which may be used in the process of the present invention with satisfactory results is alumina gel. This may be prepared by mixing equal volumes of a solution of aluminum sulphate of about 5 to 10% strength and a normal alkali solution such as sodium hydroxide or ammonium hydroxide at 0 C. or lower. Care should be taken that the reaction mass is alkaline. The jelly or gelatinous precipitate that forms is washed by decantation to free it of excess alkali and ammonium or sodium sulphate, depending upon the particular alkali employed in the formation of the precipitate.

If desired, the washed gelatinous precipitate may be peptized as by treating same with a suitable peptizing agent to thereby form a jelly-like reaction mass which in final form exhibits superior adsorptive properties. 5 w

The jelly is then dried in a current of air at C. Before charging the refrigerating apparatus with the alumina gel it is activated at 375 to 400 C. to reduce the moisture content to a low point, say not more than 10% of the dry product by weight.

It has been foundthat alumina-silica gel is not injured by ammonia or an amine when this combination is employed in the adsorption refrigeration cycle, evidently because the water present has a greater aflinity for the alumina than the ammonia or amine, so that no injurious reaction occurs. The alumina-silica gel may be prepared in any suitable manner, for example, by thoroughly intermixing washed alumina hydrogel with washed silica hydrogel, such mixture then being squeezed through an extruding machine and the product dehydrated or dried in the usual manner so that the end product or mixed gel is a hard, porous adsorbent. Usually alumina gel is a poorer-adsorbent than silica gel, and for this reason it is preferred that the alumina shall not be present in an amount greater than about 10% or so of the weight of the silica.

As an example of a method of making an alumina-silica gel the following may be given. A washed silica hydrogel prepared in the manner above described or in any other suitable manner, and an alumina jelly is prepared as previously described. The silica hydrogel and alumina jelly are then thoroughly intermixed in the pro portions of not more than 1 part of alumina jelly to 10 parts of silica hydrogel by weight. This mixture is then extruded through an orifice and dehydrated or dried by heating in a current of air at 125 C., which, after some time, may be increased to 400 C. Before installation in the refrigerating apparatus, this plural gel preferably is activated at 375 to 450" C. for about 3 hours to reduce the moisture content to a point not much greater than about 5% by weight of the dry product, although with this silica-alumina gel the refrigeration cycle will operate successfully for long periods with a higher moisture content in the gel.

In the above example other metal oxide gels, as chromium oxide gel, may be substituted for the alumina gel. v

The term evaporating" as used herein is intended to apply to any means for causing vapor to form from a liquid, whether by heat, or expansion through an orifice, or otherwise.

In the claims, the term amo" is used to designate both ammonia and an amine.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is;

l. A method of refrigeration consisting in evaporating liquid amo and adsorbing the gaseous amo, in a solid, porous adsorbent material having the moisture content reduced to a point not exceeding 5% of its dry weight.

2. The method according to claim 1 wherein the adsorbent is a material having a pore structure similar to a gel.

'3. The method according to claim 1 wherein the adsorbent material is a hard, porous gel.

4. The method according toclaim 1 wherein the adsorbent material comprises silica gel.

5. A method of refrigeration consisting inv evaporating liquid amo and adsorbing the gaseous amo, in a highly porous dried gel prepared under acidic conditions, the moisture content of the dried gel being below 5% of its dry weight.

6. The method according to claim 5 wherein the gel is silica gel. I

7. A method of refrigeration consisting in evaporating liquid amo and adsorbing the gaseous amo, in a highly porous dried gel prepared under alkaline conditions.

8. The method of refrigeration consisting in activating silica gel at a temperature between 375 and 450 C., charging the same into refrigeration apparatus containing an anhydrous liquid amo, evaporating the liquid and adsorbing the gaseous amo in the silica gel and thereafter activating the gel at a lower temperature to remove the amo for further evaporation.

9. The method of refrigeration consisting in evaporating liquid amo and adsorbing the gaseous amo in silica gel originallyactivated to a temperature between 375 C. and 450 C. a

10. The method according to claim 9 with the step, after the adsorption, of activating the silica gel at a lower temperature to remove the amo for condensation and re-adsorption.

ERNEST B. MILLER. GERALD C. CONNOLLY. 

